Sealing nut with nylon insert

ABSTRACT

A sealing nut having a shouldered insert of heat stabilized-lubricated nylon with a protruding crown, locked into a recess provided at one end of the nut body by means of a coined lip engaging the shoulder. Sealing is effected when the nut is engaged on a threaded male member and screwed against a bearing surface through which the male member extends by exterior folding of the crown upon itself and confining the resulting fold within the lip, said lip being brought into metal-to-metal engagement with the bearing surface.

BACKGROUND OF THE INVENTION

The invention herein is concerned generally with sealing nuts and moreparticularly with a sealing nut having the ability to withstandextremely high pressures.

The particular environment in which the nut of the invention is intendedfor use is one which poses stringent requirements. The environmentcomprises a hydraulic chamber which is subject to internal pressuresabove 20,000 p.s.i. having a threaded stud or other threaded memberextending through a threaded passageway in the wall of the chamber, itbeing desired from time to time to rotate the threaded stud for reasonswhich are of no concern to this invention. Hydraulic fluid deterioratesmany substances; the environment may be subject to heat which may reachover 90° C; the nut may have to be loosened and tightened often; thepressure may have to be contained over a considerable length of time.There are other considerations related to the general need for a lockingand sealing nut of this kind.

The sealing nut of the invention has a wide range of utility in otherenvironments as well as the particular one which is mentioned above,this being in connection with hydraulic brake systems for highwayvehicles.

Prior sealing arrangements have included many different types ofstructures which had various disadvantages. These need not beexhaustively discussed, but a brief mention of some will emphasize theadvantages of this invention.

The so-called elastic stop nut structure which is generally representedby the embodiment described in U.S. Pat. 2,450,694 was primarilyintended as a locking device. Its nylon insert was unthreaded so thatwhen first used the thread was formed by the act of screwing the nuthome. This gave a small degree of sealing, but only between the malethreaded member and the nut. This type of nut is not readily "spun"either in installing or removing the same since the thread-to-threadclearance at the insert is practically nothing. These nuts are not aseffective in re-use as they are for their initial use. Threading thenylon insert during manufacture substantially eliminates their lockingand sealing abilities.

The use of a non-threaded insert in large nuts makes these nutsdifficult to install and remove.

It is clear that there is no sealing ability for the elastic stop nut inany assembly of the type which has been referred to at the outset ofthis discussion, that is, at the axial end when the nut is brought intoengagement with a bearing surface through which the threaded male memberprotrudes. Washers or other means are required to effect such sealing.Besides the inconvenience of handling, such means may be destroyed orrendered non-reusable when the amount of torque applied is high as inthe case of very high pressure installations. For example, a 5/8 inchnut of the invention is installed initially with a torque of between 50and 70 foot-pounds. This will extrude many types of compounds whichwould be used as washers.

The art has gone to the confining of the sealing member, this beingdisclosed in U.S. Pat. No. 3,265,107, 3,572,414 and 3,635,272. Thesestructures utilize inserts of a material which is generally extrudablein order to press portions of the insert into engagement with thevarious parts of the assembly.

In U.S. Pat. No. 3,265,107 the sealing to be effected is in the openingof a sheet metal member and the insert is resilient, being of siliconerubber or the like. It is hence readily distortable and capable of beingconfigured to radically different shapes compared with its original one.For high pressures and an insert made of stiff nylon, even though thematerial permits a degree of cold flow, this structure would not bepractical. The type of nylon required for high pressure arrangements isnot readily compressible, if at all, and it is likely to shear beforethe metal-to-metal contact is achieved if a structure like that of thispatent were attempted. Compressing the nylon would take enormous torque.

In U.S. Pat. No. 3,572,414 the insert is made of a low durometerurethane rubber and the need for preventing almost liquid flow of thismaterial from its confining recess dictates a structure that leaveslittle of the material for sealing purposes. The use of such materialand the structure disclosed in high pressure installations would beineffectual.

In U.S. Pat. No. 3,635,272 the insert is bonded into its recess bypre-molding and then heating the nut. This is an expensive process andcould well change the physical characteristics of the nut -- especiallyif the temperature must be elevated enough to seal an insert of smallsize in a large nut. In addition to that disadvantage, the material usedis said to be nylon or other polyamide resin capable of flowing underpressure into six recesses circumferentially arranged around the nut. Astiff material such as needed in high pressure installations would notflow as readily. In an installation such as intended by this patent,where the bolt shank enters a drilled passageway and not into a threadedpassageway, if the insert were of the stiff type needed for highpressure, the corner of the passageway, although chamfered, would belikely to punch a ring out of the insert before it permits it to flow asdescribed.

The inserts of two of the above mentioned prior art patents cannot bethreaded internally unless they are bonded in place, because otherwisethey will rotate if attempt is made to tap them when the nut is tapped.Threading them apart from the nut is impractical because the threadswould not match those of the nut when assembled. Only U.S. Pat. No.3,572,414 shows the insert locked in place, and it is not internallythreaded.

As will be explained, the insert of the nut of the invention is formedindependently of the nut body and before the nut body is tapped. It isformed of a type of nylon which has a lubricant that is compounded in itprimarily for the purpose of enabling it to release readily from molds.Coincidentally, the lubricating qualities assist in the taking up of thenut during its last stages of installation. Such a material cannot bemolded and bonded into a recess as proposed by the prior art because itwill fall out. Certainly if attempted to be secured by some expensivemeans such as adhesive it cannot help but be displaced during thetapping process.

To have a substantial protruding part and still secure the insertmechanically into the nut body while at the same time providing a spacefor the displacement of the protruding part during installation is nottaught by the prior art so far as known. The displacement is asubstantial one in order to effect the seal and lock and the way ofdoing this with a stiff insert material and without raising otherproblems is also not taught in said prior art.

The structures of the prior art which involve the use of confinedinserts have not displaced one of the principal methods of assuring aseal in the high pressure hydraulic field. The method in common use atthis time involves forming a recessed seat in the surface of the bodythrough which the male threaded member is to be screwed, surrounding andcoaxially with the threaded member. An O-ring or other sealing member tobe confined is installed in the recess and adapted to be compressed bythe nut, either with or without a washer. Several such O-rings may beused. This type of structure is expensive and the O-rings must bereplaced frequently.

The invention herein is ideally suited for use in the high pressurehydraulic field, but its principles are applicable in other fields wherethe requirements to achieve sealing are not as great. This is because ofthe great economy and effectiveness. This is true aside from the factthat it eliminates the need for surface recesses, washers and O-rings.

The most important difference between the sealing nut of the inventionand the prior structures is that the substantial protrusion of theinsert (called a "crown") herein is not intended to be only extrudedand/or compressed during the take-up action of the nut, as in the priorart, but instead is folded outwardly upon itself initially. Thus, asubstantial displacement is achieved without the need for expenditure oflarge amounts of energy, meaning that great torques need not be appliedin the early stages of assembly. The crown is made relatively narrow,i.e., measured radially, so that there is enough space to enable theformation of a shoulder to provide for securement of the insert into asocket by coining a lip onto the shoulder while still leaving space(called a "gallery") for the folded end of the crown to seat. After thishas occurred and the axial end of the lip approaches the metal-to-metalcontact desired, the body of the insert is compact ready to receive thepressure for causing the necessary cold flow to effect sealing. At thistime, the maximum of torque is applied.

The manufacture of the nut is highly economical since the inserts aremolded independently in production, the nut bodies formed in a mannernot differing substantially from that used to make the bodies of elasticstop nuts, the inserts installed in the sockets, the lips coined and thenuts tapped.

As stated above, the nut of the invention is especially intended for usein the high pressure hydraulic field but its principles are alsoapplicable in circumstances where the requirements are less stringent.This should not be considered to detract from the many features andadvantages which are achieved specifically in the high pressurehydraulic field.

In order to indicate the benefits and advantages of the nut of theinvention when used in the high pressure hydraulic field there follows alist of the features achieved through the practice of the invention inthat field. In considering this list, it will be apparent that the nutof the invention is also applicable where instead of a so-called "wet"environment existing on the interior of a chamber through the wall ofwhich a threaded male member is adapted to be screwed, the environmentmay be "dry" but under gaseous pressure. Unless the gas is corrosive,the problem of the deterioration of the insert caused by hydraulicfluids and the like is eliminated.

The features which are set forth are the principal ones, there beingmany others of a minor and indirect nature (not necessarily in the orderof importance):

1. The sealing material is rugged, stiff, durable and yet has asufficient degree of flow to achieve the necessary sealing and locking.

2. There is a substantial displacement of the crown of the insertwithout requiring undue torque and without damaging the insert duringsuch displacement.

3. The insert is permanently locked into the body of the nut, this beingaccomplished by machinery and methods used to form elastic stop nuts ofconventional construction.

4. There is a space (gallery) into which the displaced portion of thecrown enters toward the end of the take-up action.

5. There is a metal-to-metal contact of the nut body against the bearingsurface after the nut has been fully taken up at which time the insertmaterial is fully confined and has been forced to flow into the areaswhere the sealing must be effected.

6. The nut and its insert are tapped with a continuous thread duringmanufacture so that the nut can be spun on the male threaded member tothe point where the actual taking up can be commenced.

6. The nut is reusable in that notwithstanding it has been torqued homeand has effected a seal and a locking, it can be unscrewed readily, isreadily backed off without the need for application of any substantialtorque and can thereafter be reinstalled with as much sealing andlocking efficiency as before.

8. The seal is such as to withstand extremely high pressures withoutleakage.

9. The nut has an indefinite shelf life since the insert material doesnot deteriorate. This also means that when installed and maintainedunder pressure for a long period of time there is no relaxation whichcould give rise to leakage because, in addition to the nature of thematerial of the insert, it is confined and not readily capable of coldflowing past the limits established by the act of compression inachieving the metal-to-metal contact.

It should again be emphasized that the economy with which the nut of theinvention can be made and its effectiveness make it well suited to formother applications in addition to sealing in the high pressure hydraulicfield.

SUMMARY OF THE INVENTION

A sealing nut having a shouldered insert with a protruding crown lockedinto a recess provided at one end of the nut body by means of a coinedlip engaging the shoulder. The insert is tapped when the nut bore istapped to form an integral threaded combination which providesunobstructed spinning during installation and removal of the nut from athreaded stud or the like. There is an annular gallery formed betweenthe inner circumference of the lip and the crown during fabricationthrough proper choice of dimensions into which the crown moves duringaxial application of pressure thereon as in turning the nut upon a studin a manner to move the said crown axially against a bearing surfacethrough which the stud extends. This movement is effected by theinversion of the crown end upon itself, resulting in a turtle-neck-likefold of the crown. The total volume and configuration of the crown aresuch that there is some compression of the insert just before the axialend of the lip engages the bearing surface, it being intended that therebe a metal-to-metal engagement when the nut has been fully torqued toits sealed and locked condition. This compression forces portions of theinsert into the thread-to-thread clearances of the stud and nut, intothe countersunk entrance to the threaded passageway of the body of thebearing surface and seals and locks the stud in place with greatefficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a locking and sealing nutconstructed in accordance with the invention, half of the nut beingshown in section and the nut being shown in the condition it has beforeit has been put into use;

FIG. 2 is a plan view of the nut of FIG. 1 taken from the bottom orinsert end thereof;

FIG. 3 is a fragmentary sectional view of the nut of the invention withportions shown in elevation, in the process of being installed intoengagement with the bearing surface of a metal body containingpressurized fluid, the nut having been partway screwed onto a threadedmale member;

FIG. 4 is a view similar to that of FIG. 3 but showing the nut of theinvention fully screwed home and sealing the joint represented by themale threaded member and the metal body; and

FIG. 5 is a fragmentary sectional view of the nut of the invention butshowing the same some time after it has been removed from a joint suchas that of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Basically the invention is concerned with a sealing and locking nuthaving an insert of a relatively stiff nylon in which the insertprotrudes and folds over upon itself when the nut is engaged against abearing surface. This gives rise to the several advantages which havebeen described and enable the nut to be made in an economical way with astructure that provides highly efficient sealing and locking.

The nut of the invention is designated 10 and shown in FIGS. 1 and 2 inits condition prior to use, after it has been fabricated. In thefabrication techniques are used which have been known in and ofthemselves and thus machinery is available for such economicalmanufacture. The nut comprises a nut body 12 having conventionalhexagonal facets 14 to enable its being engaged by a suitable spanner orwrench. There is a central threaded bore 16 whose metal threads areshown at 18 in the upper part of the nut 10 as viewed in FIG. 1. The nut10 is formed with an annular interior socket 20 defined by an annular,integral, generally axially extending wall 22 on the bottom end of thenut body 12 and a conically tapered surface 24. The recess 20 is drilledout during the fabrication of the nut body 12. The outer diameter of thewall 22 is at most slightly less than the diameter across opposite flatfacets.

In the recess there is provided an insert 26 in the form of a ring ofgenerally irregular cross section, the insert being molded independentlyof the nut body 12 and initially formed with a shoulder 28 lying in aplane normal to the axis of the nut 10. For convenience the axis isshown by a broken line and is designated 30. The insert 26 has anannular protrusion at its lower end which is called a crown 32 andextends axially beyond the wall 22 and hence protrudes substantiallyfrom the lower end of the nut 10. The axial end of the wall 22 is in theform of a hooked lip 34 that engages against the axial end of theshoulder 28 and thereby forms a gallery 36 between the crown 32 and saidlip 34. The crown end is rounded as shown at 33.

The upper end of the bore 16 is slightly countersunk at 38 and the outercorners of the nut are chamfered as at 40 in accordance withconventional design practices.

The insert 26 is permanently locked in place by the wall 22 and the lip34 and its bore 42 is threaded as at 44 with the identical thread 18.This is accomplished by assembling the nut body 12 and the insert 26with the bores 16 and 42 unthreaded and thereafter tapping both bores ina single operation.

In the manufacture of the nut 10 the body 12 is made on conventionalscrew machine apparatus independently of the insert 26. The outercircumference of the insert and the inner circumference of the wall 22at this time are of right cylindrical configuration. The wall is longerthan shown since the lip 34 is not yet formed. The dimensions are suchthat the insert 26 is readily telescoped into the recess 20 in an easyslide fit. After this preliminary assembly, the nut 10 is placed in asuitable press and the free end of the wall 22 is coined over and uponthe shoulder 28. In this process the wall 22 is constricted somewhat andthus applies internal pressure against the insert. It then assumes thegenerally slight tapered configuration which it has in the drawings.

The insert 26 is made of a relatively stiff, high durometer nylon. Thematerial which has been used for the specific application to the highpressure hydraulic field is described as heat stabilized-lubricated 66nylon. This material is sold commercially under the trademark "Zytel 103HS1L" by E. I. Du Pont de Nemours. The lubricant may be a silicone, butin any event it assists in the removal of the molded parts from theirmolds and assists in the easing of friction during installation andremoval of the nut. It is heat retardant to a temperature of about 105°C. Its stiffness and memory make it ideally suited for the purpose ofthe invention.

In the course of use of the nut 10, the crown is outwardly inverted uponitself in a turtle-neck-like fold which is then packed down into thegallery 36. Pressure upon the insert thereafter effects the sealing andlocking function.

In FIG. 3, the nut 10 has been engaged upon a threaded stud or bolt 46which in turn is engaged in a threaded passageway 48 of a body 50designed to contain some fluid 52 such as hydraulic fluid at highpressure. The stud 46 might be any form of adjusting member, mechanismoperating device or even a fastener which is required to enter theinterior of the body 50 which requires that none of the fluid 52 escapepast the stud 46 through the passageway 48. Likewise, it is desired tolock the stud 46 from rotating or vibrating loose.

According to the invention, it is intended that the nut 10 be screwedhome against the bearing surface 54 of the body 40 in such a manner asto seal and lock the joint represented by the stud 46 and the body 50.Since the threads 18 and 44 have been cut at the same time to the properdimensions and clearance to fit the thread of the stud 46, when the nut10 is first engaged on the stud 46, it will spin freely along the studto the point where the free end of the crown 32 just touches the bearingsurface 54. (It is presumed that the bearing surface 54 is metal such assteel and that the body 12 of the nut is also steel.)

The next step in the procedure of tightening the nut is to apply awrench or spanner to the facets 14 and turn the nut clockwise (lookingdown onto the surface 54 for a right-hand thread). The first thing thathappens is that the crown 32 starts to spread radially outward as it isforced against the bearing surface 54. This is assisted by the roundedend 33 sliding on the surface 54. This condition about half-way throughthe tightening process is shown at 32-A in FIG. 3. The inner surface ofthe crown 32 must expand slightly in order for this to occur and thecrown 32 must be capable of bending. This must be done without anybreakage for example along the roots of the threads 44 in the vicinityof the crown 32.

The 66 nylon which is used is fully capable of accomplishing this. Thedimension at X in FIG. 1 being relatively narrow compared to the overalldiameter and the axial length of the crown provides sufficientflexibility. For example, in a nut having a 5/8 inch tapped thread of 18threads per inch, the outer diameter of the crown was about 0.78 inchand the amount protruding axially beyond the lip 34 was about 0.085inch. This particular nut was one which used a so-called heavy pattern,the dimension across the flats of the facets 14 being about 1.05 inch.

Continuing with the explanation of the inversion of the crown 32, thetorque which is required to start this inversion is relatively less thanthe final torque which will be applied. It is less than that which wouldbe required to crush the insert and thereby force it to flow intointerstices where it might be desired. The application of torque iscontinued until the crown 32 is fully pressed into the gallery 36 asshown at 32B in FIG. 4. Just before the end of the lip 34 engages thesurface 54, the complete fold has taken place and the line of fold isshown at 56. This has been referred to as a turtle-neck-like fold. Itresults from an inversion of about 90° for the crown 32, which while itis not a complete reverse fold is nevertheless quite substantial for asynthetic resinous material and unique, so far as known, for any type ofnut insert.

The volume of the crown 32 that will be pressed into the gallery 36 ischosen, easily by trial and error, to be more than enough to fill thegallery before the free end of the lip 34 engages the bearing surface54. This means that as the last turn or turns of the wrench are beingapplied, the body of the insert 26 has tremendous pressure applied to ittending to make it expand. Through cold flow, the material of the insert26 is forced into the threads of the stud 46 in the area 58; into theclearance space between the threads 18 and the threads of the stud 46 inthe area 60; and also into the countersink 62 that is formed in theentrance of the passageway 48. This effects both a sealing and a lockingof the stud 46 in place.

In a joint such as described, using a 5/8 × 18 sealing nut of thedimensions mentioned above, that is, with the heavy design of the nutbody 12, withstood over 30,000 p.s.i. in a test of hydraulic equipmentwithout failure or leakage.

The nut of the invention is reusable, as explained. Thus, if the stud 46has to be turned temporarily, the nut 10 may be backed off until theinsert is relieved of pressure after which the stud may be rotated andthe nut 10 retorqued to seal and lock with substantially the sameeffectiveness as before. It has been found that after the nut has beenin place and under pressure for a period of time it can be completelyremoved from the joint and later reused. The configuration of the insertis changed, but not to a degree that renders the nut useless. Due to theremarkable "memory" of polyamide resin, the crown 32 will slowly tend toreturn towards its original configuration, although it may never reachthe same.

In FIG. 5 there is shown a nut 10 which has the configuration of a crownat 32C which had been compressed to its folded condition and subjectedto very substantial pressures for a period of time. It will be notedthat the fold 56 has now opened up and can be seen at 56A and that thereis an annular protrusion at 62A. This represents the portion of theinsert that was forced into the countersink 62.

The nut 10' can be reused effectively on the same joint from which itwas removed.

Considerable variations are capable of being made in the structure ofthe invention without departing from the spirit or scope as defined inthe appended claims.

What it is desired to secure by Letters Patent of the United Statesis:
 1. A sealing nut which is adapted to be screwed onto a male threadedstud or the like and brought into axial end engagement with the bearingsurface of a body through which the stud threadedly extends in order toseal the joint defined by the stud and body and to lock the nut onto thestud while the joint is so sealed, the nut comprising:A. a nut body ofmetal having a central independently fabricated insert of a relativelystiff, high durometer polyamide resin arranged coaxially therewith andat one end thereof, B. the body and insert being locked together andthere being a continuous threaded bore in the nut with a portion of thebore being in the body and a portion of the bore being in the insert, C.the insert having a shoulder at an axial end thereof and the body havingan integral, generally cylindrical wall terminating at said one end inan angular radially inwardly bent over lip engaging the shoulder toprovide for said locking of said insert, said insert additionally havingan axially extending, integral relatively thin crown adjacent the insertbore and having at least a portion of said threaded bore on the innersurface of said crown which is spaced radially inward from the lip toprovide an annular axially facing gallery between lip and crown, D. thelip being the limit to which the nut body extends axially at said oneend, E. the axial length of the crown before the nut has been used beingsuch that the free end thereof is spaced substantially beyond the lip inan axial direction away from the nut body, F. the crown being invertedin a radially outward direction when pressed axially against a bearingsurface by screwing said nut towards said surface such action tending toproduce a turtle-neck-like fold and bringing a substantial portion ofthe crown end into the gallery to occupy substantially all of saidgallery.
 2. A nut as claimed in claim 1 in which the volume of thegallery and the volume of the folded portion of the crown are so relatedthat there is insufficient space for all of said folded portion when thenut has been screwed against the bearing surface with the lip inmetal-to-metal engagement with said surface, the resulting pressure onsaid insert forcing it to cold flow into available interstices.
 3. A nutas claimed in claim 2 in which the resin is nylon.
 4. A nut as claimedin claim 2 in which the resin is a heat stabilized-lubricated 66 nylon.5. A nut as claimed in claim 1 in which the free end of the crown isrounded.
 6. A nut as claimed in claim 1 in which the insert has anexterior cylindrical surface and an annular flat surface at said axialend which is in a plane normal to the axis of the threaded bore, thecrown protruding out of the flat surface at the radial inner edgethereof, the shoulder being formed by the juncture of the cylindricalsurface and flat surface, the cylindrical wall of the body being inengagement with the exterior cylindrical surface of the insert and thelip engaging onto the outer edge of the annular flat surface so that thegallery is formed on the unobstructed portion of the annular flatsurface.
 7. The nut as claimed in claim 6 in which the resin is a heatstabilized-lubricated 66 nylon.
 8. A sealing nut which is adapted to bescrewed onto a male threaded stud or the like and brought into axial endengagement with the bearing surface of a body through which the studthreadedly extends in order to seal the joint defined by the stud andbody and to lock the nut onto the stud while the joint is so sealed, thenut comprising:A. a metal nut body having a generally conventional solidaxial end and having an annular socket provided at its second axial end,the nut body having a through axial bore, the annular socket beingi.symmetrical with respect to the axis of the bore, ii. formed by theinterior cylindrical surface of an axially extending generallycylindrical wall integral with said nut body and a second interiorsurface of the body which intersects with said interior cylindricalsurface whose radius extends generally at an angle with the axis of thebore, iii. open to the second axial end of the nut body and to the borealong the axial length of the socket, B. an annular symmetrical,independently fabricated insert of relatively stiff polyamide resinlocked into the socket and having its exterior surface and its firstaxial end facing the solid axial end of the nut body configured snuglyto seat against the interior cylindrical surface and the second interiorsurface of said body, said inserti. having a central axial bore formedas a continuation of the bore of said nut body, both bores beingthreaded by a continuous thread, ii. having a relatively flat annularsurface formed at its second axial end providing a shoulder on theradially outer edge thereof and an annular axially extending crown atthe radially inner edge thereof, C. the free end of the axiallyextending cylindrical wall of the nut body being bent over the shoulderand engaging upon a narrow area of said flat annular surface whereby toform a lip comprising the outermost extend of the metal of said nut bodyat said second axial end, and to lock the insert into the socket, D. thecrown being radially spaced from the lip and having at least a portionof said threaded bore on the inner surface of said crown whereby toprovide a gallery between the lip and the crown upon the flat annularsurface of the insert, E. the crown extending in a radial direction awayfrom the solid axial end of the nut body substantially beyond the lip,and F. the crown being folded outwardly when axial pressure is appliedto the end thereof so that it inverts and is forced into the gallery. 9.A sealing nut as claimed in claim 8 in which the leading end of thecrown is rounded.
 10. A sealing nut as claimed in claim 8 in which thevolume of the portion of the crown which is adapted to be forced intothe gallery is somewhat greater than the volume of the gallery wherebyto cause cold flow of other parts of the insert when all of the saidportion of said crown is forced into said gallery.
 11. A sealing nut asclaimed in claim 8 in which said first axial end of the insert and thesecond interior surface of the body are of conforming conicalconfiguration with the taper of the cone decreasing toward the solidaxial end of the nut body.
 12. A sealing nut as claimed in claim 8 inwhich the polyamide resin is a 66 nylon.
 13. A sealed jointcomprising:A. a metal body containing a fluid under pressure and havinga threaded passageway extending through a wall of the body from theinterior to the exterior thereof, B. a threaded member engaged in saidpassageway and having a stud-like portion on the exterior thereof, C.the body having a planar bearing surface surrounding the passageway onthe exterior thereof, D. a combined sealing and locking nut threadedlyengaged on the stud-like portion and having one axial end thereof inmetal-to-metal engagement with said bearing surface, said nutcomprising:i. a nut body having a socket in the one axial end, ii. apolyamide resin independently fabricated insert of substantial stiffnesslocked into the socket, there being a continuous threaded bore throughthe body and insert, the insert having a narrow annular extension havingat least a portion of said threaded bore on the inner surface of saidextension engaged against the bearing surface and inverted in an outwardfold, iii. the nut body having a lip around the socket engaged upon andlocking the insert in place, the lip providing the said metal-to-metalcontact there being an annular gallery between the lip and the extensioninto which the outward fold is pressed and confined between the lip andstud-like portion, but said gallery being somewhat less in volume thansaid fold so that in the process of screwing the nut against the bearingsurface the insert is subjected to compression force which cold flowsportions of said insert against the stud-like portion and intoclearances between said stud-like portion on the one hand and threads ofthe nut body and the threaded passageway on the other hand.
 14. A sealedjoint as claimed in claim 13 in which there is a countersink at theentrance to the threaded passageway on the exterior of the body and aportion of said insert also flows into said countersink.
 15. A sealedjoint as claimed in claim 13 in which said polyamide resin is 66 nylon.